//730 for csgo, 2 for contextid, true for tradableOnly
//This will load a user's inventory or you can use it for your own inventory (optional), but there's loadInventory which is used to get your own client's inventory.
manager.loadUserInventory(YOUR_TARGET_STEAMID, 730, 2, true, function (err, inventory, currencies) {
if (err) {
console.log(err.message);
} else {
console.log(inventory);
}
});
More information can be found here. Best regards UKF